A metalloporphyrin structure, a synthesis method thereof and application thereof in electrocatalytic oxygen reduction

Abstract

The application provides a metal porphyrin structure, a synthesis method thereof and application in electrocatalytic oxygen reduction, and belongs to the technical field of electrocatalyst preparation; on the basis of triphenylamine regulation, a lone pair electron group is introduced to obtain a metal porphyrin structure, and then the metal porphyrin structure is loaded on carbon nanotubes, carbon black and graphene oxide to obtain a metal porphyrin composite electrocatalyst of the metal porphyrin in an acidic and alkaline medium; the metal porphyrin composite electrocatalyst has the characteristics of simple synthesis and preparation method, low cost, high repeatability, green and environment-friendly production process and the like; the metal porphyrin composite electrocatalyst has excellent ORR performance, can be used for electrocatalytic oxygen reduction, and has good practicability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrocatalyst preparation, and particularly relates to a metal porphyrin structure, a synthesis method thereof and application thereof in electrocatalytic oxygen reduction. BACKGROUND

[0002] Energy devices such as fuel cells and zinc-air batteries can efficiently convert the chemical energy of fuel into electrical energy, and are one of the key development directions in the current energy field. However, as the most critical part of the related technology application, the electrocatalyst for oxygen reduction reaction is still mainly based on noble metal nanomaterials. In the prior art, the mass ratio of the electrocatalyst for oxygen reduction reaction is 10-70% of platinum, and the high cost seriously limits the popularization of related battery technology.

[0003] Metal porphyrin is considered to have the potential to replace noble metal electrocatalysts due to its wide existence in nature and easy derivatization. The porphyrin macrocycle can be simply modified in structure to change the electron density distribution on the molecule, thereby improving the interaction between the porphyrin and the carrier, the charge state on the catalytic interface, the metal-oxygen bond energy, the oxygen-oxygen bond energy and other transition state properties in the oxygen reduction reaction, so as to obtain an efficient oxygen reduction electrocatalyst. In the prior art, a multifunctional electrocatalyst is obtained by compounding an aromatic ring containing a heteroatom linkage as a substituent group with acetylene black. However, this method needs to be polymerized under solvent thermal conditions for a long time, the length of the heteroatom chain cannot be controlled, and the heteroatom has large steric hindrance, so the yield of porphyrin is low. In addition, the introduction of a triphenylamine group into the porphyrin increases the probability of collision with protons in the solution, effectively promoting oxygen reduction. However, the single triphenylamine functional group has limited regulation effect on the porphyrin, and the related organic catalytic composite still has problems such as high overpotential and low electron transfer number, and cannot completely replace the noble metal catalyst. Therefore, it is necessary to develop a new metal porphyrin structure and use it for electrocatalytic oxygen reduction. SUMMARY

[0004] In view of the problems in the prior art, the application provides a metal porphyrin structure, a synthesis method thereof and application thereof in electrocatalytic oxygen reduction. The metal porphyrin structure is obtained by introducing a lone pair electron group on the basis of triphenylamine regulation, and then the metal porphyrin structure is loaded on carbon nanotubes, carbon black and graphene oxide to obtain a metal porphyrin composite electrocatalyst for the metal porphyrin in acidic and alkaline media. The metal porphyrin composite electrocatalyst has the characteristics of simple synthesis and preparation method, low cost, high repeatability and green production process. The metal porphyrin composite electrocatalyst has excellent ORR performance, can be used for electrocatalytic oxygen reduction, and has good practicability.

[0005] In order to achieve the above technical purposes, the following technical means are adopted in the application.

[0006] The present application provides a metal porphyrin structure which is a metal porphyrin structure containing a symmetric lone pair of electrons group substituted by a para-position of triphenylamine;

[0007] The structural formula is as follows:

[0008]

[0009] In the structural formula, R1 includes a lone pair of electrons group and a derivative group thereof;

[0010] R2 is Wherein n is 0-2;

[0011] M is cobalt, iron or nickel.

[0012] Preferably, the metal porphyrin structure contains triphenylamine and a derivative group thereof and a lone pair of electrons group.

[0013] Preferably, the lone pair of electrons group includes any one of carboxylic acid, cyanoacetic acid, thiophene, pyridine, furan, pyrimidine, 2,1,3-benzothiadiazole and a derivative group thereof.

[0014] Preferably, the metal porphyrin structure includes the metal porphyrin structures shown in structural formula 1-6:

[0015]

[0016] The present application also provides a synthesis method of the metal porphyrin structure, which comprises:

[0017] (1) mixing compound II, tetracarboxylic acid methyl borate, tetrakis(triphenylphosphine)palladium, tetrahydrofuran and potassium carbonate to obtain a mixed solution, and performing a first condensation reaction on the mixed solution under stirring, to obtain a first intermediate A after the reaction; the structural formula of the compound II is R2-Br;

[0018] Mixing compound III, pyrrole and dilute hydrochloric acid to perform a second condensation reaction, to obtain a second intermediate B after the reaction; the structural formula of the compound III is

[0019] (2) uniformly mixing the first intermediate A, the second intermediate B and anhydrous dichloromethane, then adding trifluoroacetic acid dropwise to perform a first stirring reaction, adding tetrachlorobenzoquinone to perform a second stirring reaction after the reaction, adding a small amount of triethylamine after the reaction, and finally obtaining a third intermediate C;

[0020] (3) refluxing the third intermediate C in chloroform, then adding a metal salt, continuously refluxing and stirring, extracting, and purifying to obtain the metal porphyrin structure; the metal salt includes a nickel salt, a cobalt salt or an iron salt.

[0021] Preferably, in step (1), the compound II, tetracarboxymethyl borate, tetrakis(triphenylphosphine)palladium, tetrahydrofuran are used in a ratio of 1-3 mol: 1.5-5 mol: 0.1-2 mol: 5-15 mL; and the final concentration of potassium carbonate in the mixed solution is 0.1-0.5 M.

[0022] The first condensation reaction is carried out under stirring for 5-20 h in the dark under N2 protection.

[0023] The structural formula of the first intermediate A is

[0024] Preferably, in step (1), the compound III, pyrrole and dilute hydrochloric acid are used in a ratio of 1-2 mmol: 5-8 mmol: 15-25 mL; and the concentration of dilute hydrochloric acid is 0.1 M-0.4 M.

[0025] The second condensation reaction is carried out under stirring for 5-30 h in the dark under N2 protection.

[0026] The structural formula of the second intermediate B is

[0027] Preferably, in step (2), the first intermediate A, the second intermediate B, anhydrous dichloromethane, trifluoroacetic acid, tetrachloroquinone and triethylamine are used in a ratio of 0.5-2 mmol: 0.5-2 mmol: 50-300 mL: 1-10 mmol: 1-5 mmol: 1-5 mmol.

[0028] The first stirring reaction is carried out at room temperature for 1-5 h.

[0029] The second stirring reaction is carried out at room temperature for 1-5 h.

[0030] The structural formula of the third intermediate C is

[0031]

[0032] Preferably, in step (3), the third intermediate C, chloroform and a metal salt are used in a ratio of 0.01-1 mmol: 1-50 mL: 0.1-10 mmol.

[0033] The reflux stirring is carried out for 5-60 min.

[0034] The cobalt salt includes cobalt acetate or cobalt chloride; the iron salt includes ferric chloride or ferrous chloride; and the nickel salt includes nickel nitrate or nickel acetylacetonate.

[0035] The application also provides a metal porphyrin composite electrocatalyst, wherein the metal porphyrin structure is compounded with a semiconductor; the loading amount of the metal porphyrin structure is 0.01-1 wt%, and the semiconductor comprises any one of carbon black, carbon nanotubes or graphene oxide.

[0036] Preferably, when the metal porphyrin structure is compounded with carbon black, the metal porphyrin composite electrocatalyst is an irregular approximately spherical polyhedron.

[0037] When the metal porphyrin structure is compounded with carbon nanotubes, the metal porphyrin composite electrocatalyst is tubular.

[0038] When the metal porphyrin structure is compounded with graphene oxide, the metal porphyrin composite electrocatalyst is flaky.

[0039] The application also provides a synthesis method of the metal porphyrin composite electrocatalyst, comprising the following steps:

[0040] Any one of carbon black, carbon nanotubes or graphene oxide is mixed with a metal porphyrin, then a solvent dichloromethane is added, and the mixture is uniformly mixed by ultrasonic and dried to obtain a composite;

[0041] The composite is added into a mixed solution composed of diluted Nafion, and the mixture is uniformly mixed by ultrasonic to obtain a metal porphyrin composite electrocatalyst.

[0042] Preferably, the ratio of the semiconductor to the metal porphyrin is 5-100 mg: 1-5 mg.

[0043] The polymer content in the Nafion solution is 0.001-0.1 wt%.

[0044] The application also provides an application of the metal porphyrin structure or the metal porphyrin composite electrocatalyst in electrocatalytic oxygen reduction.

[0045] The lone pair of electrons, the partial charge and the like of an element or a group can effectively generate electrostatic force or intermolecular force on a charged ion in an electrolyte solution, affect the local ion concentration of a catalyst molecule, change the charge state and reaction potential barrier of a ground state molecule or a transition state. On the basis of the triphenylamine regulation, the application introduces a lone pair of electrons, which can effectively adsorb protons in a solution, generate and promote the proton-coupled electron transfer process at a catalytic interface, is expected to increase the number of electron transfer and promote four-electron reduction; on the other hand, the lone pair of electrons can regulate the electron cloud density of the porphyrin central metal and form a stronger pi-pi* stacking with a carbon carrier, which can effectively improve the electrocatalytic oxygen reduction activity, reduce the oxygen reduction potential and improve the reaction current density.

[0046] The interface charge separation and migration ability of the metalloporphyrin structure of the application is related to the electron-donating ability of the substituent group, and the metalloporphyrin structure is a symmetrical metalloporphyrin structure containing a para-substituted triphenylamine and an upper and lower group containing a lone pair of electrons, compared with the metalloporphyrin structure in the prior art. The special structure can effectively improve the oxygen reduction performance of the porphyrin and promote the interface charge separation of the catalysis.

[0047] The application synthesizes a metalloporphyrin composite electrocatalyst based on the metalloporphyrin structure, and the metalloporphyrin exposes more active sites to carbon black, carbon nanotubes and graphene oxide, and can improve the utilization rate of porphyrin molecules. The metalloporphyrin composite electrocatalyst has a reduction potential and a corresponding current density close to Pt / C, which proves that the synergistic effect of the lone pair electron group and the triphenylamine group can effectively improve the oxygen reduction effect, and provides a possible solution for engineering efficient production of metalloporphyrin as an electrocatalyst.

[0048] The metalloporphyrin in the metalloporphyrin composite electrocatalyst is loaded on a carbon material, and the main morphology of the loading material has no obvious change, and the morphology structure has no obvious effect on the electrocatalytic performance. The metalloporphyrin structure and the metalloporphyrin composite electrocatalyst have the characteristics of simple synthesis and preparation method, low cost, high repeatability, green and environmentally friendly production process and the like. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 The metalloporphyrin composite electrocatalyst preparation flowchart.

[0050] Figure 2 The scanning electron microscope images of the metalloporphyrin / carbon black composite electrocatalyst (a), the metalloporphyrin / carbon nanotube composite electrocatalyst (b) and the metalloporphyrin / graphene oxide composite electrocatalyst (c).

[0051] Figure 3 The cyclic voltammogram of different metalloporphyrin composite electrocatalysts obtained in 0.1M KOH.

[0052] Figure 4 The linear sweep voltammogram of different metalloporphyrin composite electrocatalysts obtained in 0.1M KOH. DETAILED DESCRIPTION

[0053] The application will be further described below in combination with the drawings and specific examples, but the protection scope of the application is not limited thereto.

[0054] Example 1: Synthesis of metalloporphyrin structure and metalloporphyrin / carbon black composite electrocatalyst

[0055] I. Synthesis of metalloporphyrin structure:

[0056] The flow chart of synthesizing the metalloporphyrin structure is shown as follows:

[0057]

[0058] The specific synthesis steps are as follows:

[0059] (1) Synthesis of the first intermediate A:

[0060] 2 mmol of 4-bromo-N,N-triphenyl aniline, 2.2 mmol of 4-formyl phenyl boronic acid, 0.1 mol of tetrakis(triphenylphosphine)palladium, 10 mL of tetrahydrofuran and 10 mL of 0.4M potassium carbonate were added into a flask to obtain a mixed solution, and the mixed solution was stirred for 12 hours in the dark and under nitrogen atmosphere. Yellow first intermediate A was obtained by vacuum distillation and silica gel column chromatography (dichloromethane: petroleum ether = 1:1).

[0061] The first intermediate A is 4'-(diphenylamino)-[1,1'-biphenyl]-4-carboxaldehyde, and the yield is 91%.

[0062] (2) Synthesis of the second intermediate B:

[0063] 60 mmol (4.2 mL) of pyrrole was added into a 500 mL two-neck flask, 200 mL of freshly prepared 0.18M HCl was added, and the mixture was stirred under nitrogen protection until it was uniformly mixed, then 10 mmol (2.2 g) of 4-(5,5-dimethyl-1,3-dioxan-2-yl)benzaldehyde was added, and the second condensation reaction was carried out at room temperature for 12 hours. After the reaction was completed, the reaction solution was extracted with dichloromethane, and the lower organic phase was collected.

[0064] Anhydrous sodium sulfate was added to the organic phase to dry it, and then filtered. Silica gel powder was added, and the rotary evaporator was used to spin dry to obtain a crude product. The crude product was purified by silica gel column chromatography (dichloromethane: petroleum ether = 1:1), and then recrystallized to obtain white solid, which was the second intermediate B. The second intermediate B is 2,2'-((4-(5,5-dimethyl-1,3-dioxan-2-yl)phenyl)methylene)bis(1H-pyrrole).

[0065] (3) Synthesis of the third intermediate C:

[0066] To 1 mmol (349.43 mg) of the first intermediate A and 1 mmol (334.32 mg) of the second intermediate B were added in 100 mL of the solvent anhydrous dichloromethane, obtaining a mixture. The mixture was stirred in the dark, under nitrogen atmosphere, for 5 minutes, until it was well mixed, then 2.42 mmol (0.18 mL) of trifluoroacetic acid was slowly added to initiate the reaction, after stirring the reaction at room temperature for 1 h, 1.5 mmol (393.3 mg) of tetrachloro-1,4-benzoquinone was added and it was stirred under the same conditions for another hour of reaction, after the end of the reaction, 2.42 mmol (0.337 mL) of triethylamine was added to neutralize the reaction, obtaining the crude product.

[0067] The crude product was purified by column chromatography on silica gel (dichloromethane: petroleum ether = 1:2) to obtain a solid, the third intermediate C, which is 4',4"'-(10,20-bis(4-(5,5-dimethyl-1,3-dioxan-2-yl)phenyl)porphyrin-5,5-diyl)bis(N,N-diphenyl-[1,1'-biphenyl]-4-amine), with a yield of 14.4%.

[0068] (4) Synthesis of the metalloporphyrin structure:

[0069] 0.05 mmol (66.483 mg) of the third intermediate C was dissolved in 15 mL of chloroform, then 9 mL of trifluoroacetic acid and 1 mL of water were added to it, the reaction was stirred vigorously, then triethylamine was added to neutralize it to basicity, then it was purified and dissolved in 4.5 mL of tetrahydrofuran and 4.5 mL of glacial acetic acid, then 1 mmol (77 mg) of ammonium acetate was added, it was refluxed for 6 hours and extracted with 100 mL of water.

[0070] The extracted product was dissolved in chloroform, refluxed at 68°C for 15 minutes, then 0.25 mmol (40.55 mg) of iron chloride in 9 mL of methanol was added in a double-necked flask with a syringe, under continuous reflux and stirring, the reaction was monitored by TLC, the organic phase was collected by extraction with dichloromethane and water. Then the organic phase was dried over anhydrous sodium sulfate, an appropriate amount of silica gel powder was added, and it was concentrated into a dry powder by vacuum distillation, finally the powder was purified by column chromatography on silica gel (dichloromethane: petroleum ether = 1:2) to obtain a dark red solid, the metalloporphyrin structure.

[0071] The metalloporphyrin structure is (2E,2'E)-3,3'-((10,20-bis(4'-(diphenylamino)-[1,1'-biphenyl]-4-yl)iron porphyrin-5,5-diyl)bis(4,1-phenylene))bis(2-cyanoacrylic acid): yield: 86%, denoted as porphyrin 1.

[0072] II. Synthesis of the metalloporphyrin composite electrocatalyst:

[0073] The porphyrin 1 prepared in (I) is combined with carbon black to synthesize a metal porphyrin composite electrocatalyst, and the synthesis process is shown in Figure 1 The synthesis process is shown in the following.

[0074] 3mg of porphyrin 1 and 10mg of carbon black are placed in a 10mL glass bottle, and an appropriate amount of dichloromethane (DCM) is added. After ultrasonic treatment for 30 minutes, drying is performed to obtain a composite. 1mg of the dried composite is placed in a mixed solution composed of 100μL of water, 100μL of ethanol, and 8μL of 5% Nafion, and ultrasonic treatment is performed for 30min to obtain the metal porphyrin composite electrocatalyst, which is recorded as porphyrin 1 / carbon black composite electrocatalyst.

[0075] Figure 2 The scanning electron microscope image of (a) porphyrin 1 / carbon black composite electrocatalyst is shown in the figure, from which it can be seen that,

[0076] The porphyrin 1 / carbon black composite electrocatalyst is spherical, and the morphology of the porphyrin 1 / carbon black composite electrocatalyst does not change significantly compared with the morphology of the semiconductor under the condition that the iron porphyrin doping amount is relatively small.

[0077] Example 2: Synthesis of metal porphyrin structure and metal porphyrin / carbon nanotube composite electrocatalyst

[0078] I. Synthesis of metal porphyrin structure:

[0079] The synthesis process of the metal porphyrin structure in this example is shown in the following:

[0080]

[0081] According to the process shown, the synthesis steps of the metal porphyrin structure in this example are basically the same as the synthesis steps of porphyrin 1 in Example 1, and the only difference is that the formyl phenyl boronic acid in step (1) is replaced by (4'-formyl-[1,1'-biphenyl]-4-yl)boronic acid, and the 4-(5,5-dimethyl-1,3-dioxan-2-yl)benzaldehyde in step (2) is replaced by 4-pyridine carboxaldehyde. The obtained 4”,4””-(10,20-di(pyridin-4-yl)iron porphyrin-5,15-diyl)bis(N,N-diphenyl-[1,1':4',1”-triphenyl]-4-amine) is recorded as porphyrin 2.

[0082] II. Synthesis of metal porphyrin composite electrocatalyst:

[0083] The porphyrin 2 prepared in (I) is combined with carbon nanotubes to synthesize a metal porphyrin composite electrocatalyst, and the synthesis steps are shown in the following:

[0084] 3mg of porphyrin 2 and 10mg of carbon nanotube were placed in a 10mL glass bottle, and an appropriate amount of dichloromethane (DCM) was added. After ultrasonic treatment for 30 minutes, drying was performed to obtain a composite. 1mg of the dried composite was placed in a mixed solution consisting of 100μL of water, 100μL of ethanol, and 8μL of 5% Nafion, and ultrasonic treatment was performed for 30min to obtain the metalloporphyrin composite electrocatalyst, which was denoted as porphyrin 2 / carbon nanotube composite electrocatalyst.

[0085] Figure 2 Figure 6 is a scanning electron microscope image of (b) porphyrin 2 / carbon nanotube composite electrocatalyst. As can be seen from the figure, the porphyrin 2 / carbon nanotube composite electrocatalyst is mainly in a tubular shape, and the morphology of the porphyrin 2 / carbon nanotube composite electrocatalyst does not change significantly compared with the morphology of the semiconductor in the case of a relatively small amount of iron porphyrin doping.

[0086] Example 3: Synthesis of metalloporphyrin structure and metalloporphyrin / graphene oxide composite electrocatalyst

[0087] I. Synthesis of metalloporphyrin structure:

[0088] The flow of the synthesis of the metalloporphyrin structure in this example is shown as follows:

[0089]

[0090] According to the flow shown, the synthesis steps of the metalloporphyrin structure in this example are basically the same as the synthesis steps of porphyrin 1 described in Example 1, and the only difference is that 4-(5,5-dimethyl-1,3-dioxan-2-yl)benzaldehyde in step (2) is replaced by 2-thiophene formaldehyde, and cobalt acetate tetrahydrate is used instead of iron chloride in step (3). The obtained 4',4"'-(10,20-di(thiophene-2-yl) cobalt porphyrin-5,15-diyl) bis(N,N-diphenyl-[1,1'-biphenyl]-4-amine) is denoted as porphyrin 3. The yield of the metalloporphyrin 3 is 60%.

[0091] II. Synthesis of metalloporphyrin composite electrocatalyst:

[0092] In this step, the metalloporphyrin composite electrocatalyst was synthesized by combining the porphyrin 3 prepared in (I) with graphene oxide, and the specific synthesis steps are shown as follows:

[0093] 3mg of porphyrin 2 and 10mg of carbon nanotube were placed in a 10mL glass bottle, and an appropriate amount of dichloromethane (DCM) was added. After ultrasonic treatment for 30 minutes, drying was performed to obtain a composite. 1mg of the dried composite was placed in a mixed solution consisting of 100μL of water, 100μL of ethanol, and 8μL of 5% Nafion, and ultrasonic treatment was performed for 30min to obtain the metalloporphyrin composite electrocatalyst, which was denoted as porphyrin 2 / carbon nanotube composite electrocatalyst.

[0094] Figure 2 The (c) is a scanning electron microscope image of the porphyrin 3 / graphene oxide composite electrocatalyst, from which it can be seen that the porphyrin 3 / graphene composite electrocatalyst is mainly in the form of a sheet. In the case of a relatively small amount of cobalt porphyrin doping, the morphology of the porphyrin 3 / graphene composite electrocatalyst does not change significantly compared with the morphology of the graphene semiconductor.

[0095] Example 4: Test of the electrocatalytic oxygen reduction performance of the metal porphyrin composite electrocatalyst

[0096] In this example, the electrocatalytic oxygen reduction performance of the metal porphyrin composite electrocatalyst prepared in Examples 1-3 was tested, and the specific test process is shown as follows:

[0097] Cyclic voltammetry, linear sweep voltammetry and rotating disk electrode tests were carried out in a 0.1M potassium hydroxide solution, so as to test the oxygen reduction activity potential and selectivity and other performances of the three kinds of porphyrin-coated carbon nanotube, carbon black and graphene oxide composite materials. The test results are shown in Figures 3-4 and Table 1. All curves in O2-saturated electrolyte are background current subtracted from double-layer capacitance by recording corresponding curves using N2-saturated solution under the same experimental conditions.

[0098] The test results are shown in Figures 3-4 and Table 1.

[0099] Figure 3 The (c) is a scanning electron microscope image of the porphyrin 3 / graphene oxide composite electrocatalyst, from which it can be seen that the porphyrin 3 / graphene composite electrocatalyst is mainly in the form of a sheet. In the case of a relatively small amount of cobalt porphyrin doping, the morphology of the porphyrin 3 / graphene composite electrocatalyst does not change significantly compared with the morphology of the graphene semiconductor.

[0100] Table 1. Electrochemical catalytic oxygen reduction performance of the composite electrocatalyst

[0101]

[0102] Figure 4The linear sweep voltammograms of different metal porphyrin composite electrocatalysts in 0.1M KOH can be seen from the figure, and the limiting current density increases with the increase of the rotating speed, which is mainly due to the increase of the diffusion rate of oxygen in the electrolyte with the increase of the rotating speed. Table 1 is the oxygen reduction performance parameters of the composite catalyst. Among them, the porphyrin 3 / graphene oxide composite material has the most excellent oxygen reduction performance, and the limiting current density can reach-5.00mA cm -2 at a rotating speed of 900. The starting potential and half-wave potential of the porphyrin 3 / graphene oxide composite material are 0.98V and 0.90V, followed by the porphyrin 2 / carbon nanotube composite material (0.97V, 0.89V), and then the porphyrin 1 / carbon black composite material (0.95V, 0.86V). The three kinds of composite electrocatalysts are close to or slightly better than the existing commercial catalyst Pt / C (0.1M KOH, the limiting current density is about-4.90mA cm -2 at a rotating speed of 900, the starting potential is about 0.98V, and the half-wave potential is about 0.89V), so the metal porphyrin composite electrocatalyst has excellent oxygen reduction performance.

[0103] In summary, the metal porphyrin composite electrocatalyst is synthesized based on the structure of the metal porphyrin, and the metal porphyrin composite electrocatalyst has the characteristics of being firm and easy to derive; the molecular structure is changed by structural modification on the basis of porphyrin, thereby affecting the electron density distribution on the molecule, the interaction between porphyrin and the carrier, the charge state on the catalytic interface, and the strength of the metal-oxygen and oxygen-oxygen bond, thereby improving the electrocatalytic oxygen reduction performance; the metal porphyrin composite electrocatalyst has the characteristics of simple synthesis and preparation method, low cost, high repeatability, green and environmentally friendly production process, etc.; the metal porphyrin composite electrocatalyst has excellent oxygen reduction performance, and is a new type of platinum-free catalyst that can be practically used for oxygen reduction.

[0104] The embodiments are preferred embodiments of the present application, but the present application is not limited to the above embodiments, and any obvious improvements, replacements or modifications made by those skilled in the art without departing from the essential content of the present application shall fall within the protection scope of the present application.

Claims

1. A metalloporphyrin structure, characterized by, The metalloporphyrin structure is a metalloporphyrin structure containing a symmetric lone pair of electrons group substituted by triphenylamine para-position; The structural formula is: In the structural formula, R1 includes a lone pair of electrons group and its derivative group; R2 is wherein n is 1-2; M is cobalt or iron; the metalloporphyrin structure contains triphenylamine and a lone pair of electrons group; The lone pair of electrons group is selected from any one of cyanoacetic acid, thiophene, pyridine and furan.

2. The method of synthesizing the metalloporphyrin structure according to claim 1, characterized in that, The synthesis method comprises: (1) mixing compound II, tetracarboxyformyl methyl borate, tetrakis(triphenylphosphine)palladium, tetrahydrofuran and potassium carbonate to obtain a mixed solution, and performing a first condensation reaction on the mixed solution under stirring, to obtain a first intermediate A after the reaction is completed; the structural formula of the compound II is R2-Br; The first intermediate A has a structural formula of The compound III, pyrrole and dilute hydrochloric acid are mixed to carry out a second condensation reaction, and a second intermediate B is obtained after the reaction is completed; the structural formula of the compound III is The structural formula of the second intermediate B is (2) uniformly mixing the first intermediate A, a second intermediate B and anhydrous dichloromethane, then adding trifluoroacetic acid dropwise to perform a first stirring reaction, adding tetrachlorobenzoquinone to perform a second stirring reaction after the reaction is completed, adding a small amount of triethylamine after the reaction is completed, and finally obtaining a third intermediate C; The structural formula of the third intermediate C is: (3) refluxing the third intermediate C in chloroform, then adding a metal salt, continuously refluxing and stirring, extracting, and purifying to obtain the metalloporphyrin structure; the metal salt is selected from cobalt salt or iron salt.

3. The method of synthesis of claim 2, wherein, In step (1), the use amount ratio of the compound II, tetracarboxyformyl methyl borate, tetrakis(triphenylphosphine)palladium and tetrahydrofuran is 1-3 mol: 1.5-5 mol: 0.1-2 mol: 5-15 mL; and the final concentration of potassium carbonate in the mixed solution is 0.1-0.5 M; The first condensation reaction is performed under the following conditions: stirring and reaction for 5-20 h in a dark environment under N2 protection; The use amount ratio of compound III, pyrrole and dilute hydrochloric acid is 1-2 mmol: 5-8 mmol: 15-25 mL; and the concentration of the dilute hydrochloric acid is 0.1 M-0.4 M; The second condensation reaction is performed under the following conditions: stirring and reaction for 5-30 h in a dark environment under N2 protection.

4. The method of synthesis of claim 2, wherein, In step (2), the use amount ratio of the first intermediate A, the second intermediate B, anhydrous dichloromethane, trifluoroacetic acid, tetrachlorobenzoquinone and triethylamine is 0.5-2 mmol: 0.5-2 mmol: 50-300 mL: 1-10 mmol: 1-5 mmol: 1-5 mmol; The first stirring reaction is performed under the following conditions: reaction for 1-5 h at room temperature; The second stirring reaction is performed under the following conditions: reaction for 1-5 h at room temperature.

5. The method of synthesis of claim 2, wherein, In step (3), the use amount ratio of the third intermediate C, chloroform and the metal salt is 0.01-1 mmol: 1-50 mL: 0.1-10 mmol; The refluxing and stirring time is 5-60 min; The cobalt salt is selected from cobalt acetate or cobalt chloride; and the iron salt is selected from iron chloride or ferrous chloride.

6. A metalloporphyrin composite electrocatalyst characterized in that, The metalloporphyrin composite electrocatalyst is obtained by compounding the metalloporphyrin structure of claim 1 with a semiconductor; the loading amount of the metalloporphyrin structure is 0.01-1 wt%, and the semiconductor is selected from any one of carbon black, carbon nanotube and graphene oxide.

7. The method for the synthesis of the metalloporphyrin composite electrocatalyst according to claim 6, characterized by the fact that, The synthesis method comprises: Any one of carbon black, carbon nanotube or graphene oxide is mixed with metalloporphyrin, then dichloromethane is added, and the mixture is uniformly mixed by ultrasonic and dried to obtain a composite; The composite is added into a mixed solution of diluted Nafion, and the mixture is uniformly mixed by ultrasonic to obtain a metalloporphyrin composite electrocatalyst.

8. The method of synthesis of claim 7, wherein, The ratio of the semiconductor to the metalloporphyrin is 5-100 mg: 1-5 mg; The content of the polymer in the Nafion solution is 0.001-0.1 wt%.

9. The metalloporphyrin structure of claim 1 or the metalloporphyrin composite electrocatalyst of claim 6 is applied in electrocatalytic oxygen reduction.

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